The invention relates to the fuel management of internal combustion engines. More particularly, the invention relates to a fuel or fuel mixture shutoff mechanism which is installed for the purpose of preventing the unintentional combustion in the cylinders of the engine after ignition shutoff, i.e. so-called "dieseling". In known engines and fuel management systems for motor vehicles, there are provided idle cutoff mechanisms which, for example, block off the idle jet in the carburetor and thus prevent dieseling.
In fuel injection systems, it is known to connect the exciter coil of fuel injection valves in series with a semiconductor element which is driven, in most cases, by a driver transistor or driver stage.
It has been further proposed, for example in U.S. Patent application Ser. No. 794,885, the contents of which are hereby expressly incorporated into the present application, to provide an rpm-dependent circuit ahead of the driver circuit so as to perform the idle fuel or idle mixture shutoff in carburetors when the engine is being overrun, i.e. during engine braking. The rpm-dependent circuit responds when a particular engine speed is reached and energizes a magnetic shutoff valve which insures that the fuel supply to the engine is not interrupted when the engine is actually and intentionally idling. the known system proposed in the aforementioned patent application Ser. No. 794,885 further includes a pressure switch, preferably a vacuum switch, disposed in association with the induction tube and intended to monitor the position of the throttle. This vacuum switch also causes actuation of the magnetic valve in certain states. The present invention relates particularly to the input portion of the aforementioned apparatus and constitutes an improvement of a variety of aspects of this system.